In my personal opinion:
Time and place - designating a city and a day is not the same as two people agreeing to meet at the ABC parking lot at 123 Main Street at 1:00pm today - seems like no time and place were set.
Done deal - When the other party (not the one who said deal) starts to re-negotiate and says:
"Would you happen to have the original handguards, grip and magazine for it? Box and papers?"
"How about this. Leave the rail on it and keep the (2) tapco mags in exchange, give me the factory handguards, steel mag and factory pistol grip. Fair?"
"Sounds good. In a perfect world, I would like the factory grip, mag, quad rail and factory handguards. Let's talk in the morning."
These items all re-open the negotiations and at that point there is no longer a 'done deal'.
My opinion is that no deal terms or time/place was finalized and no negative feedback is justified...YMMV .
The deal was done. If they say I'll take it. It stands like it's advertised, and agreeing on a city to meet sounds pretty firm. (This gives the buyer and seller some estimated amount of mileage that will be involved in the deal)
Some deals just ain't going to happen if folks aren't willing to meet somewhere in between, and at the onset of a deal a specific address and time for the transaction would be asking a little much. (I usually handle this with phone conversations and will not leave for a meet unless we have talked on the phone just prior to leaving for the meeting place.)
Asking about other accessories after you state "done deal" shouldn't void the deal or make it any less binding.
I'll take it/done deal, if you'll change the stocks, throw in a couple of mags., and some ammo, is not a deal that's a negotiation.
I've had people waste my time that had high FB with a 100% positive and a high post count.
It is a waste of time trying to coordinate with people to meet and then they sell it to their neighbor.
I've had people tell me they would take it and the deal not be completed for several weeks.( I'm usually not in a hurry, just so long as I'm not being jerked around waiting is not a problem)
The problem is some people are trying to sell something so they can pay their power bill. (First one here with the cash)
If you walk up to a guy and tell him that you are going to kick his ass, and then start to negotiate with him about tying one of his hands behind his back and blind folding him, and you get to use a ball bat, you probably just toted an ass whoopin.
I say done deal, If you want to back out on a deal at least be man enough to contact the other party and let them know your intentions. If you act like a man with integrity, then most likely you'll be treated that way.